Well pump is a kind of general mechanism and widely used in many fields. The pump, adapted to set device above water level, mainly includes two types, one is submersible pump and the other is well pump.
Working principle of the submersible pump is: an electrical motor for the submersible pump is a submersible motor; both of pump body and electrical motor are under water during working. Therefore it has high requirement for sealing ability of the motor and it causes high cost and difficulty of maintaining. Furthermore, the submersible pump has a larger radial size, so its range of usage is restricted because it can not be put into some well with small radial size.
There are two kinds of well pump: multistage well pumps and jet well pumps. A pump body and an electrical motor of the multistage well pump are separated, the pump body is adopted a multistage centrifugal pump which is submersible, and the electrical motor is disposed on ground. A coupler is installed between the pump body and the electrical motor, usually the shaft of the pump is segmentary connected due to its long length. Therefore, this pump not only requires highly accuracy of manufacture and high cost, but it also has problems of complex installation, high failure rate and difficulty of maintaining, and it is hard to be widely applied.
Therefore, jet well pump has been a primary pump used for deep pumping. However, state of the art jet well pumps present some drawbacks. A jet well pump assembly was disclosed in Chinese utility model CN2231721 (App. No. 95218415.X), this assembly includes an electrical motor assembly arranged on external well, a jet pump assembly arranged inside of the well and a connection pipe between both of them. Wherein the jet pump assembly includes a jet pump, a filter pipe, a check valve, a vacuum meter and connecting pipe; the electrical motor assembly includes a base, a centrifugal pump, a circulation water tank, a pressure meter and valves of inlet and outlet. The circulation water tank and the centrifugal pump are mounted on the base, and connected by a connection pipe. The centrifugal pump and the jet pump are connected by a connecting pipe, i.e. return pipe, which forms a high pressure flow filled into the jet pump and ejected out through a nozzle of the jet pump; a connection pipe (i.e. inlet pipe) is also disposed between the water tank and the jet pump, the flow ejected from the nozzle enters in the water tank through this pipe. Thereby, such jet well pump assembly not only makes the total size of the system huge which bring inconveniences on transport and usage, but it also increases the cost due to installation of circulation water tank and other accessories (such as the connection pipes, the pressure meter, the valves of inlet and outlet).
Another Chinese utility model CN2308738 disclosed a Spray-sucking deep well water pump. This well pump includes an electrical pump with an auto-sucking screw pump, an inlet valve, a water tank, a pressure meter, a pressure controlling outlet valve, Spray-sucking head and bottom valve, an inlet and outlet of the Spray-sucking head, i.e. jet pump, respectively connected to an inlet and outlet of the electrical pump with an auto-sucking screw pump through an inlet pipe and a high pressure return pipe. Although this jet well pump eliminates a circulation water tank existed in the prior art, which increases its flexibility, however there is a store tank to increase the water pressure of the return pipe, because that it is necessary to compensate the insufficiency of pressure for ejection of using the electrical pump with an auto-sucking screw pump; on the other hand, an upper portion of the inlet pipe is connected to the inlet pipe of the electric pump with an auto-sucking screw pump (not a body of the pump), which increases a complexity of structure and causes there is no enough suction power inside of the inlet pipe so as to decrease total water power of the pump.
Furthermore, usually each part of the jet well pumps in the prior art is manufactured by casing, which causes problems of huge size, heave weight and absence of flexibility. On the other hand, the casing is a process having problems of high consuming of electricity and material, intensity of labor and unfriendly influence for environment; and casing process also can not make some components for those smaller centrifugal pumps, such like an impeller having a narrow outlet and small flow rate, due to restriction of size and structure.